1. Field of the Invention
This invention relates to a recording apparatus applicable as an output device of a computer, facsimile and the like. More in particular, the present invention relates to a transfer type recording apparatus capable of controlling image density without increasing energy consumption and complication in structure.
2. Description of the Prior Art
The recording process of the type which carries out the steps of forming a toner layer of a predetermined thickness, forming an electrostatic latent image on the thus formed toner layer and transferring the latent image onto a recording medium is well known in the art. One such example is disclosed in the Japanese Laid-open Publication No. 55-84955.
In accordance with the process disclosed in the above-mentioned publication, a toner layer uniformly charged to a first polarity and having a predetermined thickness is formed on the surface of a donor roller which is driven to rotate at a constant speed. Then the toner layer is selectively charged to a second polarity opposite to the first polarity thereby forming an electrostatic latent image. Thereafter, the latent image is transferred onto a transfer or recording medium thereby forming a visible toner image thereon. Such a recording process is quite advantageous since it is simple and easy to carry out.
It has however been required to further improve the control over image density of a reproduced image. It is true that image density may be increased by applying an increased recording potential. But, this will also increase power consumption and require the provision of a higher power unit, which is economically disadvantageous. Thus, there has been a need for improving the control over image density of a reproduced image without significantly increasing the level of power consumption.